Why you need GTLS

GTLS (Gaseous Tritium Light Source) is the most reliable form of illumination utilised in watches.

On this page you will find the key facts about GTLS and why we use it in all of our watch models.

Key Features

All of our watches contain GTLS illumination, providing you with the most reliable illumination available on the market.

GTLS is a completely safe and reliable form of illumination – The electron emitted by tritium is so low in energy that it is unable to penetrate the human skin.

The T rating relates to the total watch radiation content, measured in millicuries. We offer both T25 and T100 GTLS watches.

The GTLS illumination used in Nite Watches is supplied by mb-microtec of Switzerland , the original founders and market leaders of the technology.

GTLS come in a range of colour variants which are offered by Nite Watches including green, orange, blue and white.

GTLS technology does not require sunlight or any form of external power source in order to operate.

Superluminova illumination will fade over a short period of time whereas, GTLS illumination will remain constant throughout.

If green is 100% visible to the human eye, then white and ice blue are 60% and orange is 40%

The GTLS glass vials are sealed by specially modulated CO2 lasers

The science behind GTLS

Tritium, also known as super heavy hydrogen, was first discovered by Ernest Rutherford, ML Oliphant and Paul Harteckin in 1934.

Tritium emits electrons through beta decay and when these electrons interact with a phosphorous material, a fluorescent light is created that can last up to 20 years. When this tritium powered illumination is sealed inside a glass tube, it is known as a GTLS (Gaseous Tritium Light Source) which is up to 100 times brighter over a long period than any comparable technology.

To produce a GTLS vial, glass is lined with phosphorescent material, then filled and pressurised by a machine with gaseous tritium and sliced into segments by a laser beam to be sealed hermetically.

Inside the vial, the electrons emitted by the tritium gas excites the phosphor to give off the cold continuous light. GTLS can be created in different colours, generally green is perceived by the human eye as the brightest colour.

Based on green (100%), the brightest output of the other colours is as follows; ice blue 60%, white 60%, orange 40%. Blue GTLS, is often used in diving watches as it remains visible at up to 60m/187 feet in depth – longer or deeper than any other colour.

“Unlike other luminous watch's that die down after a few hours, this stays bright all night - very bright.”

Seamus McCabe 28/04/14

“I must say I was very impressed with the build quality and the performance of the tritium tubes when dark. This is possibly the best watch I have ever owned.”

Mohit 07/10/14

“The illumination of the hands and numerals is excellent. You really get a good comparison when you set it beside a standard watch with illuminated hands. There is no comparison in the dark.”

Euan McDonald 29/12/13

“the GTLS tubes provide a perfect level of illumination for use in low light and total darkness.”

Matt 03/01/14

“Sure I have a digital watch with press illumination but it's just an hassle compared to the quick glance that's required for this”

Ron Wallace 15/11/14

T25 vs T100 Illumination

We offer both T25 and T100 GTLS watches. The T rating refers to the total watch radiation content which is measured in millicuries.

All watches with a T25 rating contain up to 25mCi of radiation content and similarly, watches with a T100 rating, contain above 25mCi and up to 100mCi. Whilst there are differences between the amount of mCi in the T25 and T100 models, the idea of “which is better” is simply a choice of preference and taste.

If you have any concerns about the safety of GTLS technology, the electron emitted by tritium is so low in energy that it is unable to penetrate the human skin.

It has also been shown that consuming 1 banana every other day causes the same dose as breaking a GTLS equipped watch (1GBq of activity) and absorbing 100% of its tritium content (mb-mictrotec).